1. Technical Field of the Invention
The invention relates to determining position information of a mobile terminal in a mobile communications system.
2. Description of Related Art
A number of (end-user) applications require a fairly accurate physical position of the end-user. An example of such an application is a location-based service, wherein a service is provided to a mobile terminal user, dependent of the geographical position of the mobile terminal. In a mobile communication system such as the Global System for Mobile Communications (GSM) the position of a mobile terminal may be determined by measuring the distance to several Radio Base Stations (RBSs). This requires measurement by one or more RBS. A lot of messaging in the network in relation with these measurements may be unnecessary. The reason for this is that an RBS is not able to establish independently whether a mobile terminal is moving or not. Therefore there is a chance that a position is measured of a non-moving mobile terminal. Depending on the intervals between a first and a second measurement, the unnecessary load on the network will increase. For example patent application WO03/065698 aims at reducing unnecessary measurements by the RBS by having a mobile terminal determining its own location and sending a trigger when a predetermined area is entered. The positioning by the mobile terminal is done using e.g. positioning systems to be used by the mobile terminal itself. One example of such a positioning system is Global Positioning System (GPS).
WO03/065698 further proposes a monitoring engine that monitors the location of the mobile terminal and of other contacts specified in associations, and checks for the user-specified trigger-events. This feature is split out into a proximity server, which is an operating system platform feature. A proximity server makes use of whatever location technologies and quality criteria are available on the phone. The proximity server has 2D and 3D geometry calculation engines that carry out and optimise the calculations necessary for checking for trigger-events. A mobile terminal may register its trigger events at the proximity server. Trigger events may be described in terms of named landmarks or as geometrical areas. The Mobile terminal may receive notifications in return when the trigger event is detected.
Current solutions provide for a trigger whenever one mobile terminal moves relative to a fixed object or area. There is no method or system for initiating triggers when a first moving mobile terminal is in the proximity of a second moving mobile terminal, of which the movement and/or direction is unknown to the first mobile terminal.